This invention relates to oil wells and more particularly to an automatic well cutoff system for pumping oil wells.
In the production of oil, a well is drilled to the oil bearing strata. At the bottom of the well, a pump is installed to pump oil to the surface of the earth from the pool that gathers at the bottom of the well. A desirable mode of operation is to pump the oil whenever there is sufficient oil in the pool and to stop the pumping when there is not sufficient oil in the pool.
Advantages of this desirable mode of operation are that the pump automatically reaches its optimum pumping rate with a result in a saving of man hours and equipment. The pump thus operates at a greater efficiency in pump displacement, thereby reducing the total number of pumping hours which in itself results in a saving of power and power cost.
Those in the prior art have long recognized the desirability of control systems for providing such an automatic pump-off control of oil wells. Examples of such prior art include U.S. Pat. No. 2,550,093 to G. A. Smith and U.S. Pat. No. 2,316,494 to R. Tipton. In the Smith patent, a valve activates an electrical circuit which causes the pump to be shut down after a predetermined time interval in the event the produced oil ceases to flow through the valve. In the Tipton patent, a clock is caused to run in response to there being no produced fluid, thus causing the pump to periodically cycle in response to the well being pumped dry.
These two patents exemplify the prior art in that various means and systems are provided which monitor the lack of produced fluid and which in turn cause the system to recycle in response thereto.
However, the prior art, to the best of my knowledge, has failed to provide a system which provides satisfactory pumpoff control for the various oil well pumping facilities having varying conditions and components thereof.
A need therefore exists in the oilfield for a means for controlling the operation of oil well pumps in such a manner that the duration of their pumping periods will be substantially or approximately in accordance with the actual time periods required for the pumping off of the wells. Such a need exists for a means of control whereby an oil well can continue in operation so long as it is pumping oil, but which will automatically stop when it has pumped off the oil, or for breakage, in response to cessation of discharge of oil from the pump.
It is therefore the primary object of the present invention to provide a well pumping control system wherein the pump control is a factor of the percentage of time during which oil is being pumped during a given period;
It is also an object of the invention to provide a new and improved well pumping control system wherein the operation of the pump is automatically stopped when the fluid in the borehole is depleted;
It is a further object of the invention to completely shut off the system after a predetermined number of shut-down cycles should proper flow not be reestablished; and
Another object of this invention is to provide a system having a variable timing subsystem providing greater flexibility than heretofore known in the prior art.
The objects of the invention are accomplished, generally, by a system which produces signals indicative of the normal operation of the well pumping installation which are used in conjunction with timing circuitry which determines the percentage of time of normal operation during a given time period, and based upon such determination, either allows the system to continue or to shut down. As additional features of the invention, means are provided for the system to recycle and to completely shut down after a predetermined number of nonproductive recycles.